1. Field of the Invention
The present invention relates to an inverter, and more particularly, to an inverter using an oxide semiconductor, and a driving circuit and a display device including the same.
2. Discussion of the Related Art
With the advent of an information-oriented society, various electronic devices are used, and the electronic devices include an inverter inverting polarity of input signal.
Generally, the inverter uses a CMOS circuit having low power consumption and easy design. However, the CMOS circuit has disadvantages of high production cost and complicated production process.
To solve the problems, PMOS or NMOS in enhancement mode or depletion mode is suggested. However, the PMOS or NMOS has problems of increase of power consumption and difficulty of full swing.
Recently, research of forming a transistor using an oxide semiconductor having excellent electrical property has actively progressed. The transistor using the oxide semiconductor i.e., the oxide transistor is formed only as an N type transistor because of its property of material.
The inverter formed using the N type oxide transistor is explained with reference to FIG. 1, which is a circuit diagram of an inverter using an oxide transistor according to the related art.
Referring to FIG. 1, first and second N type oxide transistors T1 and T2 constituting an inverter IV are operated in a depletion mode and an enhancement mode, respectively. By configuring the first and second transistors T1 and T2 as shown, full swing can be achieved.
However, the first transistor T1 in the depletion mode should have a thick semiconductor layer, and the second transistor T2 in the enhancement mode should have a thin semiconductor layer. To do this, two processes are required to form the transistors, and thus production cost and process increase.
The first transistor T1 may be configured to have a double gate structure and be supplied with a positive voltage. However, a process of forming an additional gate electrode is required, design margin is reduced, and additional gate signal is required.
When a gate driving circuit is formed using an NMOS inverter, a boostrap capacitor is connected to a Q node using boostrap principle. Accordingly, a voltage of the Q node rises, thus a stress is produced at a transistor in the circuit due to a high driving voltage, and thus reliability is deteriorated. Particularly, the oxide transistor is more vulnerable to stability. However, when the gate driving circuit is formed using a CMOS inverter, the boostrap is not produced, and thus reliability is achieved.
As described above, the driving circuit using the N type oxide transistor is problematic about reliability.